Studies in lipid metabolism continue to concentrate upon the composition of the lipoproteins, with particular emphasis on the lipoproteins in the human genetic disorder abetalipoproteinemia. Newly discovered peptides in the high density lipoprotein fraction have been identified and are being characterized. Implications of these findings for normal lipoprotein structure and synthesis are being studied. Tocopherol metabolism in humans and in the rat is being investigated. Particular emphasis is placed upon exchange reaction rates and extent between individual lipoprotein fractions and the red cells. The distribution of tocopherol in lipoprotein fractions can be postulated as a result of these studies. The study of tocopherol distribution and exchange is compared with that of cholesterol; there are similarities noted in both parameters with the HDL fraction, but in VLDL equilibration between erythrocyte and the lipopsrotein tocopherol is not achieved in the study period. Measurement of post heparin plasma lipase activity against several substrates has been carried out in human subjects, particularly those with possibly genetic disorders of lipid metabolism. Using an inhibitor of lipase activity, it is possible to identify more than one source for plasma lipase activities, and with different substrates to identify different specificities and activities.